Broken and/or missing animation nodes?
This node has been replaced by Sound Falloff and Sound Spectrum when the falloff workflow was introduced.
Your node network should look like this :


Basically AN now generates a tweakable falloff from a music file input, in real time, there is no need to bake it anymore. The falloff can then be used to achieve a great number of effect. Here we use it to scale the pegs up and down and to change their material property so they appear to be reacting to the sound waves :